1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating a semiconductor device, and more particularly, it relates to a semiconductor device having silicide films and a method of fabricating a semiconductor device.
2. Description of the Background Art
Following recent requirements for refinement and high-speed operation of a semiconductor device, various techniques have been developed for reducing the resistance values of a gate electrode and a source/drain electrode of a transistor. As one of such techniques, a salicide (self-aligned silicide) technique of silicifying the upper portions of the gate electrode and the source/drain electrode of the transistor in a self-aligned manner is put into practice.
When the salicide technique is applied to an analog device having a capacitive element and a resistive element, however, the upper portion of a polycrystalline silicon film for the resistive element is also silicified and hence the resistance of the resistive element is disadvantageously reduced to about 2 to 5 xcexa9/. Further, a gate oxide film must be prevented from breakdown resulting from static electricity not only in the analog device but also in an input/output circuit part of a semiconductor device, for example. In general, therefore, the resistance of a high-concentration impurity diffusion layer of a source/drain region is set relatively high. When the salicide technique is applied to the semiconductor device having such an input/output circuit part, however, the upper portion of the high-concentration impurity diffusion layer of the source/drain region is also silicified and hence the resistance thereof is disadvantageously reduced.
In relation to this problem, Japanese Patent Laying-Open No. 2000-22150, for example, proposes a technique of preventing regions such as an input/output part and a resistance part requiring high resistance from silicification in a salicide process.
In general, the sheet resistance of an unsilicified silicon region is decided by impurity implantation conditions and heat treatment conditions for forming a transistor. In other words, the unsilicified silicon region can have a sheet resistance value in the range of the same value as that of a diffusion layer formed with the highest impurity concentration and the same value as that of a well region formed with the lowest impurity concentration. Further, the sheet resistance value of the unsilicified silicon region depends on the impurity concentration decided by combining impurity implantation conditions in the aforementioned range. In other words, the sheet resistance of the unsilicified silicon region must be generally decided by controlling the impurity implantation conditions for forming the transistor thereby controlling the impurity concentration.
Following recent diversification of the analog device mounted on a semiconductor device, however, extension of the degree of freedom in design is hindered if the sheet resistance value of the unsilicified silicon region is decided by the impurity implantation conditions employed for forming the transistor. Particularly when resistivity values and resistance values are previously decided in the stage of design for forming a device corresponding thereto with regulation in the stage of fabrication, the resistance value of the unsilicified silicon region must be arbitrarily decidable in the range of about 4 xcexa9/ for a general low-resistance silicide region to about 1000 xcexa9/ for a high-resistance silicide region in formation of the transistor.
An object of the present invention is to provide a semiconductor device capable of easily setting the resistance of a resistive element or the like to an arbitrary value without controlling an impurity implantation condition in formation of a transistor or the like.
Another object of the present invention is to provide a method of fabricating a semiconductor device capable of easily setting the sheet resistance of a resistive element or the like to an arbitrary value without controlling an impurity implantation condition in formation of a transistor or the like.
In order to attain the aforementioned objects, a semiconductor device according to a first aspect of the present invention comprises a first silicide film formed on a first silicon region and a second silicide film, formed on a second silicon region, consisting of the same silicide material as the first silicide film and differing from the first silicide film in film quality to have a sheet resistance value different from that of the first silicide film.
In the semiconductor device according to the first aspect, as hereinabove described, the second silicide film consisting of the same silicide material as the first silicide film and differing from the first silicide film in film quality to have a sheet resistance value different from that of the first silicide film is so provided that a silicide film having a low sheet resistance value and a silicide film having a high sheet resistance value can be easily obtained. When an impurity is introduced into the second silicide film itself so that the second silicide film differs from the first silicide film in film quality in this case, for example, a second silicide film having an arbitrary high sheet resistance value can be obtained by controlling the type of and the introduction condition for the impurity. Thus, the sheet resistance of a resistive element or the like can be easily set to an arbitrary value without controlling an impurity injection condition in formation of a transistor or the like. Consequently, the degree of freedom in design can be extended.
In the aforementioned semiconductor device according to the first aspect, the second silicide film preferably differs from the first silicide film in film quality due to introduction of an impurity, to have a higher sheet resistance value than the first silicide film. According to this structure, a second silicide film having an arbitrary high sheet resistance value can be easily obtained by controlling the type of and the introduction condition for the impurity.
A semiconductor device according to a second aspect of the present invention comprises a first silicon region and a second silicon region, a first silicide film formed on the first silicon region and a metal layer, formed on the second silicon region, having a sheet resistance value different from that of the first silicide film.
In the semiconductor device according to the second aspect, as hereinabove described, the first silicide film formed on the first silicon region and the metal layer, formed on the second silicon region, having the sheet resistance value different from that of the first silicide film are so provided that a silicide film or a metal layer having a low sheet resistance value and a metal layer or a silicide film having a high sheet resistance value can be easily obtained. In this case, the sheet resistance values of the first silicide film and the metal layer can be easily controlled to prescribed values by controlling the materials for and the thicknesses of the first silicide film and the metal layer, for example. Thus, the sheet resistance value of a resistive element or the like can be easily set to an arbitrary value without controlling an impurity implantation condition for forming a transistor or the like. Consequently, the degree of freedom in design can be extended.
In the aforementioned semiconductor device according to the second aspect, the first silicon region and the second silicon region may consist of the same silicon layer.
A semiconductor device according to a third aspect of the present invention comprises a silicon region and a silicide film, formed on the silicon region, deteriorated in crystallinity to be increased in sheet resistance.
In the semiconductor device according to the third aspect, as hereinabove described, the silicide film deteriorated in crystallinity to be increased in sheet resistance is so provided that a silicide film having a high sheet resistance value can be easily obtained. Thus, a resistive element or the like requiring a high sheet resistance value can be easily formed by the silicide film.
In the aforementioned semiconductor device according to the third aspect, the silicide film is preferably deteriorated in crystallinity due to introduction of an impurity. According to this structure, a silicide film having an arbitrary high sheet resistance value can be obtained by controlling the type of and the introduction condition for the impurity. Thus, the sheet resistance value of a resistive element or the like can be easily set to an arbitrary value. Consequently, the degree of freedom in design can be extended. In this case, the silicide film is preferably converted to an amorphous state due to introduction of the impurity. Further, the impurity may include at least one element selected from a group consisting of Ge, Si, B, As, P and BF2. In addition, the silicide film may contain Co.
A method of fabricating a semiconductor device according to a fourth aspect of the present invention comprises steps of forming a first silicon region and a second silicon region, forming a first silicide film on the first silicon region while forming a second silicide film consisting of the same silicide material as the first silicide film on the second silicon region through a first salicide process, forming a reaction inhibition film to cover the second silicide film, and forming a third silicide film consisting of the same silicide material as the first silicide film on the first silicide film provided on the first silicon region through a second salicide process.
In the method of fabricating a semiconductor device according to the fourth aspect, as hereinabove described, the reaction inhibition film is formed to cover the second silicide film and thereafter the third silicide film consisting of the same silicide material as the first silicide film is formed on the first silicide film provided on the first silicon region through the second salicide process, whereby a thick silicide film can be formed on the first silicon region by stacking the first and third silicide films. In this case, the sheet resistance value of the multilayer film formed by the first and third silicide films and that of the second silicide film can be easily controlled to prescribed values respectively by controlling the thicknesses of the first, second and third silicide films. Thus, the resistance value of a part (the region formed with the second silicide film) such as a resistive element requiring a high sheet resistance value can be easily set to an arbitrary value without controlling an impurity implantation condition for forming a transistor or the like. Consequently, the degree of freedom in design can be extended.
A method of fabricating a semiconductor device according to a fifth aspect of the present invention comprises steps of forming a first silicon region and a second silicon region, forming a first silicide film on the first silicon region while forming a second silicide film on the second silicon region through a first salicide process, forming a reaction inhibition film and an etching mask to cover the second silicide film, removing the first silicide film by etching through the etching mask, and forming a third silicide film on the first silicon region through a second salicide process.
In the method of fabricating a semiconductor device according to the fifth aspect, as hereinabove described, the reaction inhibition film and the etching mask are formed to cover the second silicide film for thereafter removing the first silicide film by etching through the etching mask and forming the third silicide film on the first silicon region through the second salicide process, whereby a third silicide film having a larger thickness or a smaller sheet resistance than the second silicide film can be formed on the first silicon region. In this case, the sheet resistance values of the second and third silicide films can be easily controlled to prescribed values respectively by controlling the thicknesses of the second and third silicide films, for example. Thus, the resistance value of a part (the region formed with the second silicide film) such as a resistive element requiring a high sheet resistance value can be easily set to an arbitrary vale without controlling the impurity implantation condition for forming a transistor or the like. Consequently, the degree of freedom in design can be extended.
In the aforementioned method of fabricating a semiconductor device according to the fifth aspect, the step of forming the third silicide film preferably includes a step of forming the third silicide film consisting of the same silicide material as the second silicide film and having a larger thickness than the second silicide film on the first silicon region. According to this structure, a third suicide film having an arbitrary low sheet resistance value and a second silicide film having an arbitrary high sheet resistance value can be easily formed.
A method of fabricating a semiconductor device according to a sixth aspect of the present invention comprises steps of forming a first silicon region and a second silicon region, forming a first silicide film on the first silicon region while forming a second silicide film on the second silicon region through a first salicide process, forming an etching mask to cover the first silicide film, and etching the second silicide film by a prescribed thickness through the etching mask.
In the method of fabricating a semiconductor device according to the sixth aspect, as hereinabove described, the etching mask is formed to cover the first silicide film for thereafter etching the second silicide film by a prescribed thickness through the etching mask, whereby the sheet resistance value of the second silicide film can be easily increased beyond that of the first silicide film. In this case, the sheet resistance value of the second silicide film can be controlled to a prescribed value by controlling the quantity of etching of the second silicide film. Thus, the resistance value of a part (the region formed with the second silicide film) such as a resistive element requiring a high sheet resistance value can be easily set to an arbitrary value without controlling the impurity implantation condition for forming a transistor or the like. Consequently, the degree of freedom in design can be extended.
A method of fabricating a semiconductor device according to a seventh aspect of the present invention comprises steps of forming a first silicon region and a second silicon region, forming a first silicide film on the first silicon region while forming a second silicide film on the second silicon region through a first salicide process, forming a mask layer to cover the first silicide film, and ion-implanting an impurity into the second silicide film through the mask layer thereby increasing the sheet resistance value of the second silicide film.
In the method of fabricating a semiconductor device according to the seventh embodiment, as hereinabove described, a first silicide film having a low sheet resistance value and a second silicide film having a high sheet resistance value can be easily formed through the steps of forming the mask layer to cover the first silicide film and ion-implanting the impurity into the second silicide film through the mask layer thereby increasing the sheet resistance value of the second silicide film. In this case, a second silicide film having an arbitrary high sheet resistance value can be formed by controlling the type of and the introduction condition for the impurity.
A method of fabricating a semiconductor device according to an eighth aspect of the present invention comprises steps of forming a first silicon region and a second silicon region consisting of the same silicon layer, forming conductive layers on the first silicon region and the second silicon region, forming a reaction inhibition film and an etching mask to cover the second silicon region and the conductive layer formed on the second silicon region, removing the conductive layer formed on the first silicon region by etching through the etching mask, and thereafter forming a first silicide film on the first silicon region through a salicide process.
In the method of fabricating a semiconductor device according to the eighth aspect, as hereinabove described, the reaction inhibition film and the etching mask are formed to cover the second silicon region and the conductive layer formed on the second silicon region for thereafter removing the conductive layer formed on the first silicon region by etching through the etching mask and thereafter forming the first silicide film on the first silicon region through the salicide process, whereby a silicide film or a conductive layer having a low sheet resistance value and a conductive layer or a silicide film having a high sheet resistance value can be easily obtained. In this case, the sheet resistance values of the first silicide film and the conductive layer can be easily controlled to prescribed values respectively by controlling the materials for and the thicknesses of the first silicide film and the conductive layer, for example. Thus, the sheet resistance value of a resistive element or the like can be easily set to an arbitrary value without controlling the impurity implantation condition for forming a transistor or the like. Consequently, the degree of freedom in design can be extended.
A method of fabricating a semiconductor device according to a ninth aspect of the present invention comprises steps of forming a silicon region, forming a silicide film on the silicon region, and deteriorating crystallinity of the silicide film thereby increasing the sheet resistance value of the silicide film.
In the method of fabricating a semiconductor device according to the ninth aspect, as hereinabove described, the sheet resistance value of the silicide film is increased by deteriorating crystallinity of the silicide film, whereby a silicide film having a high sheet resistance value can be easily obtained. Thus, a resistive element or the like requiring a high sheet resistance value can be easily formed by the silicide film.
In the aforementioned method of fabricating a semiconductor device according to the ninth aspect, the step of deteriorating crystallinity of the silicide film thereby increasing the sheet resistance value of the silicide film preferably includes a step of deteriorating crystallinity of the silicide film by ion-implanting an impurity into the silicide film. According to this structure, a silicide film having an arbitrary high sheet resistance value can be obtained by controlling the type of and the introduction condition for the impurity. Thus, the sheet resistance value of a resistive element or the like can be easily set to an arbitrary value. Consequently, the degree of freedom in design can be extended. In this case, the step of deteriorating crystallinity of the silicide film may include a step of ion-implanting an impurity into the silicide film thereby converting the silicide film to an amorphous state. Further, the impurity may include at least one element selected from a group consisting of Ge, Si, B, As, P and BF2. In addition, the silicide film may contain Co.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.